Uncertainty Analysis of Hydrological Drought Due to Record Length, Time Scale, and Probability Distribution Functions Using Monte Carlo Simulation Method

Standardized Runoff Index (SRI), as one of the well-known hydrological drought indices, may contain uncertainties caused by employment distribution function, time scale, and record length statistical data. In this study, uncertainty in SRI estimation monthly discharge data 30- 49-year lengths from Minab Dam watershed, south Iran, was investigated. Four probability functions (Gamma, Weibull, Lognormal, Normal) were used to fit cumulative at 3-, 6-. 9-, 12-, 24-, 48-month scales, with their goodness-of-fit normality evaluated K-S tests, respectively. Using Monte Carlo sampling, 50,000 generated for each event followed 95% confidence interval. The width interval uncertainty, sources investigated using miscellaneous factors. It found that maximum related Normal Lognormal distributions minimum Gamma Weibull distributions. Furthermore, increase both scale led decrease uncertainty.